*1.2.16 At time 0 a balance of amount B, is in an account earning sim- ple interest at rate i per period, paid at the end of the period. Var- ious deposits and withdrawals are made during the period, with a transaction of amount ak made at time tk for k = 1, 2,...,n where ( 0indicates a deposit to the account, and af 0indicates a deposit to the account, and af